Bjt saturation

Popular answers (1) Amit Das. Jawaharlal Nehru University. Reverse saturation current terminology is generally used in diode whereas leakage current is used in BJT. But both are more or less ...

When a vapor or liquid in a closed environment reaches an equilibrium between the amount of evaporating, condensing and returning molecules, the liquid or vapor is saturated. Saturated vapor is also known as dry vapor.VB = 4.78V V B = 4.78 V. The load line for the circuit in Example 5.4.1 5.4. 1 is shown in Figure 5.4.4 5.4. 4. Figure 5.4.4 5.4. 4: DC load line for the circuit of Figure 5.4.3 5.4. 3. Once again the proportions between voltage and current for the Q point appear to be proper when compared against the endpoints.With both junctions forward biased, a BJT is in saturation mode and facilitates high current conduction from the emitter to the collector (or the other direction in the case of NPN, with negatively charged carriers flowing from emitter to collector). The saturation region of a BJT (e.g. when turned on as a switch) corresponds to the triode/ohmic region of a MOSFET. Some authors also call the saturation region of a MOSFET the "active mode", which does match the terminology used for BJTs. But they also call the triode/ohmic region the "linear mode" which perhaps doesn't help that much because ...A Bipolar Junction Transistor (BJT) is a current-controlled semiconductor device which has three-terminals. The current in BJT is carried by both majority and minority carriers so it is known as bipolar device. The input resistance of BJT is low so it is used as an amplifier, oscillator circuits and digital circuits. Contents show.Ideal Saturation Ideal Cut-off We see that the Q-point lies closer to cut-off (VCE =15 V) than saturation (VCE =0.2 V). Hence the maximum available peak to peak output voltage swing =2( VCC − CEQ)=10.34 V. (c) The AC Model parameters are re rπ RB R0 L (d) For derivations, please see Lecture 13. (e) The BJT CE amplifier parameters are Rin Ro ...

4.26 Operation of a p-n-p BJT in saturation region. As IB is increased from ... (21) Plot the minority carrier distribution in n-p-n BJT in (a) forward active ...Figure 4.18 Saturation mode. [5] 4.4.7 DC Load Line Cutoff and saturation mode can be illustrated in relation to the collector characteristics curves by the use of a load line. Figure 4.19 shows a dc load line drawn on a family of curves connecting the cutoff point and the saturation point. The bottom of the load line is at ideal cutoff where I CA common emitter amplifier circuit has a load resistance, RL of 1.2kΩ and a supply voltage of 12v. Calculate the maximum Collector current ( Ic) flowing through the load resistor when the transistor is switched fully “ON” (saturation), assume Vce = 0. Also find the value of the Emitter resistor, RE if it has a voltage drop of 1v across it.81. A transistor goes into saturation when both the base-emitter and base-collector junctions are forward biased, basically. So if the collector voltage drops below the base voltage, and the emitter voltage is below the base voltage, then the transistor is in saturation. Consider this Common Emitter Amplifier circuit.PNP transistor is another type of Bipolar Junction Transistor (BJT). The structure of the PNP transistor is completely different from the NPN transistor. The two PN-junction diodes in the PNP transistor structure are reversed with respect to the NPN transistor, such as the two P-type doped semiconductor materials are separated by a …However, this “collector-emitter saturation voltage” will be fairly low, around several tenths of a volt, depending on the specific transistor used. ... BJT SPICE model parameters. type npn is 1.00E-16 bf 100.000 nf 1.000 br 1.000 nr 1.000. β is listed under the abbreviation “bf,” which actually stands for “beta, ...

In saturation, the following behavior is noted: * Vce <= 0.2V. This is known as the saturation voltage, or Vce(sat) * Ib > 0, and Ic > 0 * Vbe >= 0.7V Using the two states of cutoff and saturation, the transistor may be used as a switch. The col-lector and emitter form the switch terminals and the base is the switch handle. In other words,Therefore, a D.C. analysis problem for a BJT operating in the active region reduces to: find one of these values , , B C E ii ori and find one of these values or ( or ) CE ECCB BC V VV V Saturation For the saturation mode, we know all the BJT voltages, but know nothing about BJT currents! Thus, for an analysis of circuit with a BJT in ...This region is known as an area of extreme saturation. Complete step by step solution: Bipolar junction transistor (BJT): BJT is Bipolar Junction Transistor's ...This creates \(I_B\). If properly designed, this current will be sufficient to put the BJT into saturation. The BJT acts as a switch, completing the circuit between the DC supply, the LED and the current limiting resistor, \(R_C\). For this to work reliably, we have to make sure that the ratio of saturation current to base current is much less ...BJT (bipolar junction transistor) are widely used an amplifier, oscillator, switch etc. It is a current-driven device ( MOSFET is voltage driven), the output current is equal to the input current times a factor which is called Gain. A basic BJT has three pins: the Base, Collector, and Emitter.

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The transistor can be used as a switch if biased in the saturation and cut-off regions. This allows current to flow (or not) in other parts of a circuit. Because a transistor ’s collector current is proportionally limited by its base current, it can be used as a sort of current-controlled switch. In cutoff mode, the brake is engaged (zero base current), preventing motion (collector current). Active mode - is the automobile cruising at a constant, controlled speed (constant, controlled collector current) as dictated by the driver. Saturation - the automobile driving up a steep hill that prevents it from going as fast as the driver wishes.Also, it's usually defined in terms of current, not voltage. A typical definition of saturation is when \$\beta < 10\$ (or 20, or some other value). So to prove the BJT is in forward-active, you'd need to work out the base and collector currents, and show their ratio is above the threshold you've chosen to define saturation.1. Here's a typical Ic vs Vce diagram showing the saturation region of a BJT. In this case if Ib is set at 20uA and Vce varies between 0 and 2V you can clearly see that Ic will also vary from about 12mA (Vce=2V) to about 8mA @ Vce = 0.5V (very non linear) to 0mA @ Vce = 0V.A certain 2N3904 dc basis circuit with the following values is in saturation. Ib = 500 uA Vcc = 10V and Rc = 180 ohm and hfe = 150. If you increase Vcc to 15V, does the transistor come out of saturation? My attempt at a solution: Ic (sat) = (Vcc - Vce (sat))/Rc but Vce (sat) then work out whethere Ib is capable of producing Ic (sat) but Vce ...

The yellow region is the "linear", or "ohmic", or "triode" region. In the saturation region, the thick horizontal (well, slightly tilting upwards) straight lines (well, OK, curves) represent the (connected) points in the region of a particular Vgs value. So for example, the curve that the red dot sits represents the points of Vgs = 2.5V.A Bipolar Junction Transistor (BJT) is a current-controlled semiconductor device which has three-terminals. The current in BJT is carried by both majority and minority carriers so it is known as bipolar device. The input resistance of BJT is low so it is used as an amplifier, oscillator circuits and digital circuits. Contents show.To work as an open switch, a BJT operates in cut-off mode, here there is zero collector current, meaning ideally zero power is consumed by the BJT. On the other hand, to work as a closed switch, a BJT works …But usually the temperature of the BJT rises with use and so the base current will probably increase, causing the collector to pull harder on the collector load. In general ... Variation in a BJT's forward current gain compared to variation in saturation current. Hot Network Questions Travel to USA for visit an exhibition for ...Mar 10, 2021 · The yellow region is the "linear", or "ohmic", or "triode" region. In the saturation region, the thick horizontal (well, slightly tilting upwards) straight lines (well, OK, curves) represent the (connected) points in the region of a particular Vgs value. So for example, the curve that the red dot sits represents the points of Vgs = 2.5V. The AC load line is similar to the DC load line that was used for analyzing biasing circuits. As in the DC version, there will be a cutoff voltage, \(v_{CE(cutoff)}\), and a saturation current, \(i_{C(sat)}\). The AC and …Such as on the NPN BJT switch we are required to connect positive voltage to the base pin. It will forward-biased base-emitter junction on the transistor. Collector …May 5, 2014 · They are compact, lightweight and powerful enough to drive small machines accurately. They are suitable for working with lighter materials, such as plastics, thin wood and PCBs. NEMA 14: These motors are smaller than NEMA 17 and are ideal for ultra-compact CNC machines or applications where space is limited. Apr 15, 2011 · 81. A transistor goes into saturation when both the base-emitter and base-collector junctions are forward biased, basically. So if the collector voltage drops below the base voltage, and the emitter voltage is below the base voltage, then the transistor is in saturation. Consider this Common Emitter Amplifier circuit. BJT Regions of Operation To understand the three regions of operation of the transistor, consider the circuit below: The first region is called “cutoff”. This is the case where the transistor is essentially inactive. ... Using the two states of cutoff and saturation, the transistor may be used as a switch. The col-lector and emitter form the switch terminals …In saturation, the following behavior is noted: * Vce <= 0.2V. This is known as the saturation voltage, or Vce(sat) * Ib > 0, and Ic > 0 * Vbe >= 0.7V Using the two states of cutoff and saturation, the transistor may be used as a switch. The col-lector and emitter form the switch terminals and the base is the switch handle. In other words,

Solved Problems on Transistor. Basic electronics Solved problems By Sasmita January 9, 2020. Q1. A common base transistor amplifier has an input resistance of 20 Ω and output resistance of 100 kΩ. The collector load is 1 kΩ. If a signal of 500 mV is applied between emitter and base, find the voltage amplification. Assume α ac to be …

In saturation, the following behavior is noted: * Vce <= 0.2V. This is known as the saturation voltage, or Vce(sat) * Ib > 0, and Ic > 0 * Vbe >= 0.7V Using the two states of cutoff and saturation, the transistor may be used as a switch. The col-lector and emitter form the switch terminals and the base is the switch handle. In other words,Particularly, the Is saturation according to this SPICE description varies with temperature like this: What troubles me is the 1/(T1-T0) term in the exponent. Say, the saturation current is measured at 25 degrees celsius, then, when we try to determine the Is at that temperature we get Exp[1/0], which is an obvious singularity.Jun 16, 2017 · Additional most BJT's vendors define saturation region when Ic/Ib = 10 (called Forced Beta). And the most data-sheet show Vce_sat for Ic/Ib = 10. So, to be one hundred percent sure that your BJT will be in saturation region you must use this so-called forced beta technique when choosing base resistor value. $$\frac{I_C}{I_B} = 10$$ Particularly, the Is saturation according to this SPICE description varies with temperature like this: What troubles me is the 1/(T1-T0) term in the exponent. Say, the saturation current is measured at 25 degrees celsius, then, when we try to determine the Is at that temperature we get Exp[1/0], which is an obvious singularity.The transistor going into saturation isn't a property of the transistor itself, but instead a property of the circuit surrounding the transistor and the transistor, as part of it. A question about Vce of an NPN BJT in saturation region. For this circuit with ideal transistor (current controlled current source CCCS) any base current large than:Figure 3: In Saturation, Collector and Emitter are Nearly Shorted Together Using the two states of cutoff and saturation, the transistor may be used as a switch. The collector and emitter form the switch terminals and the base is the switch handle. In other words, the smallLecture 12-2 BJT Circuit Analysis • SPICE solves the system of nonlinear equations to obtain the voltages and currents • Is this circuit in the active region? Q1 Default RB 100E3Ω + 2V VIN RC 1E3Ω + 5V VCC IB 12.206 µA + VOUT 3.779 V +-VBE 779.365 mV IC 1.221 mA

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Finding the Base-Emitter Voltage in an NPN Transistor. The problem asks to find the the real value of base-emitter voltage, VBE V B E and the corresponding IC I C, and VOUT V OUT in the figure below: VCE(sat) V C E ( sat) is given but the transistor is not necessarily in saturation mode; in fact, it's likely operating in the forward active mode ...PNP Transistor. The PNP Transistor is the exact opposite to the NPN Transistor device we looked at in the previous tutorial. Basically, in this type of PNP transistor construction, the two interconnected diodes are reversed with respect to the previous NPN transistor. This produces a P ositive- N egative- P ositive type of configuration, with ...To keep the transistor out of the saturation region, the general rule of thumb is that the voltage on the collector should be more positive than the voltage on the base. That is the collector base junction is always reversed biased. A simple model for the operation of NPN and PNP BJT transistors in the active region is shown in figure 8.4.1.When both junctions are forward-biased, the transistor is in the saturation region of operation. Saturation is the state of a BJT in which I C has reached a maximum and is independent of I B. As V CC is increased, V CE increases as I C increases. This is the portion between points A and B in Fig. 9. Lecture 10: BJT Physics 16 Simplified Circuit Mode Saturation Region • In the saturation region, both junctions are forward-biased, and the transistor operates with a small voltage between collector and emitter. v CESAT is the saturation voltage for the npn BJT. No simplified expressions exist for terminal currents other than i C + i B = i E.May 22, 2022 · This creates \(I_B\). If properly designed, this current will be sufficient to put the BJT into saturation. The BJT acts as a switch, completing the circuit between the DC supply, the LED and the current limiting resistor, \(R_C\). For this to work reliably, we have to make sure that the ratio of saturation current to base current is much less ... PNP transistor is another type of Bipolar Junction Transistor (BJT). The structure of the PNP transistor is completely different from the NPN transistor. The two PN-junction diodes in the PNP transistor structure are reversed with respect to the NPN transistor, such as the two P-type doped semiconductor materials are separated by a …The transistor can be used as a switch if biased in the saturation and cut-off regions. This allows current to flow (or not) in other parts of a circuit. Because a transistor ’s collector current is proportionally limited by its base current, it can be used as a sort of current-controlled switch. • Forward and reverse active operations, saturation, cutoff. • Ebers-Moll ... becomes too large), the BJT will go into the saturation region (in the saturation.You cannot find it because there is no "Saturation current" in a real BJT. There will be many mode parameters in an Ebers-Moll model which you will be unable to find in a datasheet. Also note that there is no fixed point at which a BJT suddenly enters / goes out of saturation. It's more of a gradual thing. This behavior is not in the Ebers-moll ... ….

Now if both transistors are identical, or they are matched pairs then the reverse saturation current of both transistors will be the same. That means in that case, this current I s1 and I_(s (ref)) would be the same and in that case, we can say that, this current I c1 = I ref So, in this way using this Current Mirror, we can replicate this reference current.Shrimp can be a great source of protein and other nutrients — like iodine, selenium and omega-3s. But many traditional shrimp recipes go a bit heavy on saturated fats and a bit light on veggies and fiber.BJT is in sat when Ic<(β×Ib). for a BJT is to in saturation, we have to apply Vbe atleast .75V . ... When σ<1, then we say BJT is in Saturation. ... BJT goes deeper ...The definition of “saturation region” or “ON mode” when using a bipolar NPN transistor as a switch as being, both the junctions are forward biased, IC = Maximum, and VB > 0.7v. For a PNP transistor, the Emitter potential must be +ve with respect to the Base. This is the working of the transistor as a switch.Saturation region Lundstrom ECE 305 S16 V CE E: emitter C: collector B: base I C NPN BJT I C V BE1,I B1 I E I B saturation region EB: FB, BC: FB 5 I 0=qA E D n W B n i 2 N AB I C=I 0 e qV BEk BT(1−e−qV CEk BT) I C= 0 e qV BEk BTViewed 67k times. 21. This is what I know about NPN BJTs (Bipolar Junction Transistors): The Base-Emitter current is amplified HFE times at Collector-Emitter, so …When both junctions are forward-biased, the transistor is in the saturation region of operation. Saturation is the state of a BJT in which I C has reached a maximum and is independent of I B. As V CC is increased, V …The BJT transistor is perhaps one of the most interesting basic electronic components ever. ... The transistor operates in the active, cut-off and saturation region where its behavior changes accordingly. Depending on what the transistor is meant to do, you’ll want to keep the DC operating point in a certain region.Saturation Region: In saturation region, both of the junctions of the BJT are in forward bias. This region is used for the ON-state of a switch where; i c = i sat. I sat is the saturation current & it is the maximum amount of current flowing between emitter and collector when BJT is in saturation region. Since both junctions are in forward bias ... Mar 16, 2016 · You cannot find it because there is no "Saturation current" in a real BJT. There will be many mode parameters in an Ebers-Moll model which you will be unable to find in a datasheet. Also note that there is no fixed point at which a BJT suddenly enters / goes out of saturation. It's more of a gradual thing. This behavior is not in the Ebers-moll ... Bjt saturation, How to identify the Saturation in BJT? What is Hard Saturatio…, Since the BJT is a nonlinear device, it is hard to pinpoint an exact voltage that corresponds to saturation mode operation as opposed to active mode. Therefore, circuit analysis typically involves assigning a saturation collector-emitter voltage, \$ V_{CEsat} \$ , below which the device is said to be operating in saturation and above which the ... , When a vapor or liquid in a closed environment reaches an equilibrium between the amount of evaporating, condensing and returning molecules, the liquid or vapor is saturated. Saturated vapor is also known as dry vapor., (i) Saturation Region In this region, both BJT junctions are forward biased. V CE is small, e.g. 50-100 mV, but quite large collector and base currents (I C & I B) can ow. This region is not used for ampli cation. There is a low resistance between the C and E terminals; the BJT acts like a closed switch. Figure 4 shows an actual circuit of a BJT , Bjt Explanation Saturation. Yes, this is correct. The electric field of the depletion region (between the two junctions) can accelerate the charge carriers in the same direction as the diffusion current, and this current will be the collector-emitter current. Jan 26, 2021. #1., In cutoff mode, the brake is engaged (zero base current), preventing motion (collector current). Active mode - is the automobile cruising at a constant, controlled speed (constant, controlled collector current) as dictated by the driver. Saturation - the automobile driving up a steep hill that prevents it from going as fast as the driver wishes., A Bipolar Junction Transistor (also known as a BJT or BJT Transistor) is a three-terminal semiconductor device consisting of two p-n junctions which are able to amplify or magnify a signal. It is a current controlled device. The three terminals of the BJT are the base, the collector and the emitter. A BJT is a type of transistor that uses both ..., Mar 10, 2021 · The yellow region is the "linear", or "ohmic", or "triode" region. In the saturation region, the thick horizontal (well, slightly tilting upwards) straight lines (well, OK, curves) represent the (connected) points in the region of a particular Vgs value. So for example, the curve that the red dot sits represents the points of Vgs = 2.5V. , The saturation region of a BJT (e.g. when turned on as a switch) corresponds to the triode/ohmic region of a MOSFET. Some authors also call the saturation region of a MOSFET the "active mode", which does match the terminology used for BJTs. But they also call the triode/ohmic region the "linear mode" which perhaps doesn't help that much because ..., 1. Here's a typical Ic vs Vce diagram showing the saturation region of a BJT. In this case if Ib is set at 20uA and Vce varies between 0 and 2V you can clearly see that Ic will also vary from about 12mA (Vce=2V) to about 8mA @ Vce = 0.5V (very non linear) to 0mA @ Vce = 0V. , MOSFET Question 4: The threshold voltage of an n-channel enhancement mode MOSFET is 0.5 V. When the device is biased at a gate voltage of 3 V, pinch-off would occur at a drain voltage of: 2 V. 2.5 V. 3 V. 1.5 V. Answer (Detailed Solution Below) Option 2 : 2.5 V., Saturation region. This is the region in which transistor tends to behave as a closed switch. The transistor has the effect of its collector and Emitter being shorted. The collector and Emitter currents are maximum in this mode of operation. The figure below shows a transistor working in saturation region., Apr 15, 2011 · 81. A transistor goes into saturation when both the base-emitter and base-collector junctions are forward biased, basically. So if the collector voltage drops below the base voltage, and the emitter voltage is below the base voltage, then the transistor is in saturation. Consider this Common Emitter Amplifier circuit. , Learn the basics of small signal model for BJT in this lecture from EE105 course at UC Berkeley. You will find the derivation of the model parameters, the analysis of common-emitter and common-base amplifiers, and the comparison of BJT and MOSFET models. This lecture is in PDF format and contains 28 slides., BJT Regions of Operation To understand the three regions of operation of the transistor, consider the circuit below: The first region is called “cutoff”. This is the case where the transistor is essentially inactive. ... Using the two states of cutoff and saturation, the transistor may be used as a switch. The col-lector and emitter form the switch terminals …, To make a saturated solution of sodium chloride, find the solubility of sodium chloride in water, mix a solution of sodium chloride and water, and watch for saturation. The solubility of sodium chloride is 357 grams per 1 liter of cold wate..., Therefore, a D.C. analysis problem for a BJT operating in the active region reduces to: find one of these values , , B C E ii ori and find one of these values or ( or ) CE ECCB BC V VV V Saturation For the saturation mode, we know all the BJT voltages, but know nothing about BJT currents! Thus, for an analysis of circuit with a BJT in ..., May 22, 2022 · This creates \(I_B\). If properly designed, this current will be sufficient to put the BJT into saturation. The BJT acts as a switch, completing the circuit between the DC supply, the LED and the current limiting resistor, \(R_C\). For this to work reliably, we have to make sure that the ratio of saturation current to base current is much less ... , Bipolar Transistor. The Bipolar Junction Transistor is a semiconductor device which can be used for switching or amplification. Unlike semiconductor diodes which are made up from two pieces of semiconductor material to form one simple pn-junction. The bipolar transistor uses one more layer of semiconductor material to produce a device with ... , 12/3/2004 Example A BJT Circuit in Saturation 1/7 Example: A BJT Circuit in Saturation Determine all currents for the BJT in the circuit below. 10.0 K 2.0 K 5.7 V 10 K 10.7 V β = 99 Hey! I remember this circuit, its just like a previous example. The BJT is in active mode! Let’s see if you are correct! ASSUME it is in active mode and ENFORCE V, It's usually better to prevent saturation rather than trying to deal with it after it occurs, and a popular method is the Schottky transistor - which is an integrated structure combining a BJT and a Schottky diode from collector to base. The Schottky diode prevents saturation by diverting base current to the collector when the transistor gets ..., History of Bipolar Junction Transistors. The transistor (BJT) was not the first three terminal devices. Before transistors came into existence vacuum tubes were used. In electronics, vacuum tube triodes were used almost for half a century before the BJT’s.The light bulb invented by Thomas Edison in the early 1880’s was one of the first uses of vacuum tubes for any …, BJT is shown on Figure 2 IB IC VBE βIB B C E Figure 2. Large signal model of the BJT operating in the active region The large signal model represents a simple state machine. The two states of interest are: 1. B-E junction is forward biased, VBE =0.7 Volts, current flows and the BJT is on 2. B-E junction is off, no current flows and the BJT is off., BJT definition and characteristics. BJT transistor is a three terminal semiconductor device, based on three layers of p and n layers, with different doping concentration. BJT transistor can be two types – pnp and npn BJT transistor. Bipolar junction transistor (BJT) is characterised by three regions – base (B), collector (C) and emittor (E)., 1. BJT: Regions of Operation • Forward active: device has high voltage gain and high β; • Reverse active: poor β; not useful; • Cut-off: negligible current: nearly an open circuit; • Saturation: device is flooded with minority carriers; – ⇒takes time to get out of saturation saturation cut-off reverse forward active VBC VBC VCE ... , The minimum base current the BJT needs for saturation is: I B(min) = I C(sat) / ẞ (eq. 9) Note that I B should be significantly greater than I B(min) to be sure the BJT stays well into saturation. Finally, some inquisitive readers may be asking if there is a formula for V CE(sat). Indeed, there is, but as we’ve mentioned this quantity can usually be neglected …, The transistor can be used as a switch if biased in the saturation and cut-off regions. This allows current to flow (or not) in other parts of a circuit. ... In the above figures, the base of either BJT is not connected to a suitable …, Biasing Techniques (BJT) PDF Version. In the common-emitter section of this chapter, we saw a SPICE analysis where the output waveform resembled a half-wave rectified shape: only half of the input waveform was reproduced, with the other half being completely cut off. Since our purpose at that time was to reproduce the entire waveshape, this ..., 此時IC = βIB，電晶體工作於線性放大區，IC受控於IB，BJT可當成一訊號放大器。 三、飽和模式（Saturation）：VBE 及VBC均為順偏。連續提升IB值令使受控之IC到達一個最大的上限值，當此之時，續增IB已無法令IC再增其值，且說此BJT已達飽和狀態，現時之IC記為IC(sat)。, This post on bipolar junction transistor (BJT) explains the operating modes of the BJT transistor. How the bipolar junction transistor works in different operating modes like- active mode, saturation mode, cut off mode and reverse active mode. The transistor acts as an amplifier in active mode of operation while works as a switch in saturation mode and cutoff …, The BJT is a three terminal device and it comes in two different types. The npn BJT and the pnp BJT. The BJT symbols and their corresponding block diagrams are shown on Figure 1. The BJT is fabricated with three separately doped regions. The npn device has one p region between two n regions and the pnp device has one n region between two p regions. , Saturation Voltage. Vce(sat) When a BJT is turned on hard enough that the voltage drop in its collector load is sufficient to bring the collector potential below the base potential (in other words the base-collector junction is forward biased) it is said to be saturated. This saturation voltage is not proportional to the collector current, so ..., A bipolar junction transistor ( BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier.